Optical lenses used for eyeglasses, sunglasses, cameras, binoculars and the like increasingly require very high standards for geometry and mold replication. Frequently, these lenses are molded from durable optical grade plastics, and commonly have coatings applied to increase the usability and durability of the lens. For instance, scratch resistant coating, tints, polarizing coatings and laser protection coatings are commonly applied to optical lenses. These optical lens coatings may be applied directly to the surface of the lens as a liquid.
However, liquid lens coatings are subject to many factors that can affect the quality of the lens coating, and ultimately, the quality of the optical lens. It is not uncommon to have issues with dust, coating thickness and uniformity or other similar coating imperfections introduced during the coating process. Additionally, excessive handling of newly coated lenses and inconsistent timing between coating steps may lead to additional coating flaws and other inconsistencies in the finished lenses.
An additional issue arises when changes in coating uniformity are detected, even before the overall coating quality falls out of acceptable tolerances. The complete process of coating lenses may involve several coating steps, and may be followed by a curing and inspection process. The curing process allows the lens coatings to solidify after the final coating step. However, the time required for the curing process is such that new lenses must constantly be in process while other lenses are drying. Any detected defects in a finished lens will likely carry over to lenses that are coated after the flawed lens is inspected.
Furthermore, conditions in the coating process may gradually, over time, drift out of tolerance. The ability to detect defects before the defects fall out of tolerance requires analyzing defects trends as they develop. Prior art systems are generally open loop requiring the operator to take affirmative steps to adjust parameters within the coating process. Even over a short period of time, small defects if left unchecked, can lead to major problems. Even when the coating process if operating normally, contamination or molding defects can result in defective product.
U.S. Pat. No. 5,164,228, granted Nov. 18, 1992, to Peralta, et al., (hereinafter, Peralta) attempts to address some of these issues. Specifically, Peralta discloses an automated system for spin coating plastic ophthalmic lenses. However, Peralta does not make any provisions for automated inspection, feedback based on flaws in the coating process, or for automatically adjusting the timing between coating steps based on discovered coatings flaws. Furthermore, Peralta primarily focuses on indexing and tracking lenses in conjunction with the cold runners, or sprues, with which the lenses were molded.
What is needed is a system for coating lenses where each step of the coating process can be regulated and controlled. Preferably, this system would be automated, and allow for correction of defects through an automated process.